This section provides background information related to the present disclosure which is not necessarily prior art.
Body in white (“BIW”) refers to an automobile body's metal components (e.g., the frame, which may comprise the front section, front fenders, side walls, rear section, and rear fenders; the front door assemblies; the rear door assemblies; the engine hood; the roof; and the trunk lid) that have been joined together (e.g., by welding, hemming, clinching, bolting, and the like) in the process of automobile manufacturing, before painting and before moving parts, the engine, chassis sub-assemblies, and trim have been assembled into the automobile.
After the BIW is formed, the BIW is prepared for painting, which includes enhancing the adhesion and corrosion resistance of the surfaces of the BIW. According to some processes where phosphating the BIW is conducted to enhance adhesion, as many as eight to ten process steps are undertaken, including without limitation the following. First, the BIW is degreased, followed by rinsing the BIW, then conditioning the BIW, followed by phosphating the BIW to enhance adhesion of a subsequent corrosion resistant layer. Before the corrosion resistant layer may be applied, the BIW is again rinsed, then the phosphate layer is passivated, after which the BIW is again rinsed, and then the rinsing agent is drained from the BIW. The BIW is then ready for application of a corrosion resistant layer, which typically is accomplished by applying a polymer layer over the BIW.
Magnesium present on the BIW can behave aggressively and prevent phosphate coating formation on other metals present on the BIW, for example. Thus, other processes for preparing a BIW for painting, where the BIW has at least one surface comprising a magnesium alloy, include the following steps. First, the BIW is spray cleaned. The BIW is then cleaned yet again by dipping the BIW in a cleaning bath. After cleaning, the BIW is rinsed. The BIW is then immersed in an electrocoat paint operation tank (also known as an ELPO tank), where it is coated with an adhesion enhancing layer comprising a source of cations and oxygen and a corrosion resistance layer comprising a polymer. The BIW is then rinsed, the rinsing agent is then blown off, and the BIW is then baked in a baking oven to complete the polymerization of the polymer. Developing new streamlined processes for providing an adhesion coating and corrosion coating would be desirable.